Radio Shack TRS-80 Operation Manual page 88

Computer Graphics Operation Manual
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Sample Program
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DRAW TWO INTERSECTING CIRCLES
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CALL GRPINI
( l
>
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CALL CLS
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CALL SETXY(19l9l,19l9l>
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CALL CIRCLE(591,1,91.91,91.91,91.91>
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C DRAW SECOND CIRCLE WITH CENTER
291
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PIXELS TO THE RIGHT OF FIRST CIRCLE
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CALL SETXYR(291,91>
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CALL CIRCLE(591,1,91.91,91.91,91.91>
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END
VIEW
Sets Viewport
VIEW draws viewports on your screen. Graphics is displayed
only in the last defined viewport.
The upper-left corner of viewport is read as
(91,91>
(the
"relative origin"> when creating items inside the viewport.
All the other coordinates are read relative to this origin.
However, the "absolute coordinates" of the viewport, as they
are actually defined on the Graphics Cartesian system, are
retained in memory and can be read using VIEW as a function.
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